
def get_excel_columns():
    columns = []
    col1 = []
    col2 = []
    for i in range(26):
        col1.append(chr(ord('A') + i))

    for i in range(26):
        for j in range(26):
            col2.append(col1[i] + chr(ord('A') + j))
    return col1 + col2

print(get_excel_columns())